Squaroid



SQUAROID H. C. BOARDMAN Filed March 24, 1949 April 22, 1952 Patented Apr. 22, 1952 SQUAROID Harry'C. Boardman, Chicago, Ill., assigner to Chicago Bridge & Iron Company, va ,corporation oi' Illinois sppiieauoniuamlrzt, 1949, seriaiNasaasi 11 claims. (Cieza-a) vessels is circular in plan, rectangular and polygonal storage vessels are desirable under certain circumstances, particularly where they are to be `erected in restricted areas. The design of a rectangular or polygonal tank `presents diiliculties, particularly in designing a structure which will function equally well when full or partially full. If such vessel is designed to hold a full load of liquid, bending, sagging, and other stresses are introduced at intermediate liquid levels. The present vessel is designed to operate .satisfactorily under liquid loads at all levels.

The invention is illustrated in the accompanying drawings in which:

Fig. 1 is a top plan view of vthe storage vessel;

Fig. 2 is a vertical section along line 2-2 of Fig. 1; and

Fig. 3 is a view like Fig. 2 used to illustrate the engineering .and mathematical principles involved.

The vessel I comprises a flat top I I, a iiat bottom I2, joined by curved sidewalls I3. In the preferred embodiment shown a slight pitch is provided in the roof II to permit drainage of the roof although, for all practical purposes in computing the various stresses, the roof and bottom may be considered as being parallel `to each other. Supporting columns such as the columns I4 may be used between the top and bottom of the tank.

It will be noted that the curvature of the sidewalls I3 is not constant from top to bottom. The sidewalls are designed to have decreasing radii of curvature from top to bottom. The radius of curvature of the sidewalls is also designed so 'that the sidewalls are in equilibrium at the 2 consideration in feet. This radius normal to the sidewall.

A strut or chord I5`has its upper end connected at A to the juncture of the sidewalls I3 and the top II and has its lower end connected at B to the juncture of the sidewalls and the bottom I2. When the vessel is full of liquid the strut I5 serves to connect the top and bottom edges of the sidewalls. Inasmuch as under conditions of complete lling the top has a tendency to move downward and the bottom upwards, the strut is under compression when the vessel is full.

At the corners special stress conditions are involved, and these are met by the use of diaphragms25 which are welded to the junctions of the side walls and carried up .to the 4respective junctions of the side walls with the roof and with the bottom..

In the particular embodiment lshownit 'will be noted by reference `to Fig. 3 that the angle e formed between the top and a line tangent to the sidewalls at A is equal to the angle qi formed between the bottom and a line tangent to the sidewalls at B. When these two angles are equal the upward force exerted by the bottom of the sidewalls and the downward force exerted by the top of the sidewalls when the vessel is full are precisely equal and are carried from one to the other by the strut I5. The general equation relating this common angle to the vessels height and the side stress T is:

10H2 cos 0- cos ca in which -w and T are as in the previous equation and H is the vertical distance between the top and bottom in feet.

Theoretically the angles 0 and o can be arbitrarily given any value from zero to If the angles are zero the roof, sides and bottom would be equally stressed and the sides would be tangent tothe roof at an infinite horizontal distance from the juncture of the side and the-bottom. On the other hand, if H and care 90 the sidewalls would be vertical and hence T, which would be reiiected in the thickness required for the sidewalls, would be prohibitively great.

By virtue of the formulae given, however, the values of 0 and fp and the corresponding value of T are so chosen as to result in the minimum cost of the structure and 0 and qb can be varied so as to produce the most economical figure for T which results, of course, in the ability to use minimum plate thicknesses.

Under partial liquid loads, that is, when the vessel is only partly filled with liquid, the curve of the sidewalls is not the equilibrium curve for the liquid pressures exerted. Consequently, the side plates tend to sag downward. Accordingly, I provide a kangaroo truss IB connecting the sidewalls to the strut I5. Thus, the vertically downward force exerted by the sidewalls is carried through the truss I6 to the strut I5 and thus downward to the bottom I2. In orderto spread this additional downward force when the vessel is partially filled over a large area of the bottom, I provide the bottom with a plurality of angle irons I1 welded thereto near its outer edge, which irons are connected by means of a truss member I8 to the strut I5. When the vessel is completely filled, the strut I5 is under compression due to the tendency of the roof to move downward and the bottom to move upward at their junctions with the sidewalls, and the vertically downward'load on the foundation is constant over the entire bottom. i As the curve of the sidewalls is the equilibrium curve for full conditions, the strut I5 is the only member of the strut-truss system doing any work and the truss members'l and I8 are not performing any function. It is only when the vessel is partially lled and the curvature of the sidewalls is thus no longer the equilibrium curve for the pressures then existing that the truss members serve to support the sidewalls against sag and transmit that stress to the strut. The inwardly projecting truss member I8 spreads the vertical load carried by the strut over sutilcient area of the bottom to keep the downward pressure on the foundation I9 under all conditions of partial loading from exceeding the uniform pressure on the foundation when the vessel -is full.

Obviously, a number of strut-truss systems I5 and I6 are provided about the periphery of the vessel, the number of such systems depending to a large degree upon the strength of the individual members thereof and the size and capacity of the vessel.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications.

gonal inplan and the curvature of the sidewalls .increasing from top to bottom to equalize tension therein when the vessel is full of liquid, with the angle atthe ljuncture of the sidewalls to the roof being equal to the angle at the juncture of the sidewalls to the bottom, and strengthening means bracing each corner of the vessel.

2. A vessel for storing liquids at substantially atmospheric pressure having a flat top, a fiat bottom larger than the top,and outwardly curved sidewalls, the vessel being polygonal in plan and the curvature of the sidewalls increasing from top to bottom to equalize tension therein when the vessel is full of liquid with the angle at the juncture of the sidewalls to the roof being equal to the angle at the juncture of the sidewalls to the bottom, a diaphragm bracing each corner of the vessel, and a strut connecting the juncture 'of the sidewalls to the top to the juncture of the sidewalls to the bottom.

` 3. A vessel for storing liquids at substantially atmospheric pressure having a top, a bottom, and curved sidewalls, the vessel being polygonal in plan and the radius of curvature in feet at vertically spaced .points along said sidewalls being equal to where T is the stress in lbs. per horizontal foot of sidewall, w is the weight in lbs. per cubic foot of the liquid to be contained in the vessel, and y is the vertical distance in feet from the point under consideration on the sidewall to the top of the designed liquid level, and the angle between horizontal and the tangent to the sidewall at the designed liquid level being equal to the angle between horizontal and the tangent to the sidewall at the bottom thereof.

4. A vessel for storing liquids at substantially atmospheric pressure having a lat top, a flat bottom, and outwardly curved sidewalls, the vessel being polygonal in plan and the .curvature of the sidewalls increasing from top to bottom to equal'- ize tension therein when the vessel is full of liquid with the angle at the juncture of the sidewalls to the roof being equal to the angle at the juncture of the sidewalls to the bottom. the cosine of said angle being equal to 41; where w is the weight in lbs. per cubic foot of the liquid to be contained in the vessel, H is the vertical distance in feet between the top and bottom of the vessel, and T is the stress in lbs. per horizontal foot of sidewall.

5. A vessel for storing liquids at substantially atmospheric pressure having a iiat top, a flat bottom, and curved sidewalls, the vessel being polygonal in plan and the curvature oi the sidewalls increasing from top to bottom, the radius of curvature at vertically spaced points along said sidewalls being equal to w?! where T is the stress in lbs. per horizontal foot of sidewall, w is the weight in lbs. per cubic foot of the liquid to be contained in the vessel, and y is the vertical distance in feet between the juncture of the roof to the sidewalls and the point under consideration on the sidewall with the angle at the juncture of the sidewalls to the roof being equal to the angle at the juncture of the sidewalls to bottom, the cosine of said angle being equal to wHZ where w is the weight in lbs. per cubic foot of the liquid to be contained in the vessel, H is the vertical distance in feet between the top and bottom of the vessel, and T is the stressin lbs. per horizontal foot of sidewall, and a strut connecting the juncture of the sidewalls to the roof i the sidewalls to the roof being equal to the angle at the juncture of the sidewalls to the bottom, a strut connecting the juncture of the sidewalls to the roof to the juncture of the sidewalls to the bottom, truss members connected to the strut and the bottom, and strengthening means bracing each corner of the vessel.

7. A vessel for storing liquids at substantially atmospheric pressure having a top, a bottom extending outwardly beyond the top, and sidewalls of polygonal configuration, the sidewalls being curved from the bottom to the top to equalize tension therein when the vessel is full l of liquid, there being truss members at intervals along the sidewalls connected to a substantially straight chord, said chord being connected at its top to the junction of the sidewalls and the roof and at its bottom to the bottom of the vessel at a point outside of the vertically downward pro jection of the roof and within the vertical downwardly projection of the sidewalls, and a foundation for the vessel having a portion beneath the point of the connection of the chord to the bottom, whereby stresses induced when said vessel is partially lled with the liquid are carried outwardly and downwardly by the chords to the foundation.

8. A vessel for storing iiquids at substantially atmospheric pressure having a top, a bottom extending outwardly beyond the top, and sidewalls, the sidewalls being curved from the bottom to the top to equalize tension therein when the vessel is full of liquid, there being truss members at intervals along the sidewalls connected to a substantially straight chord, said chord being connected at its top to the junction of the sidewalls and the roof and at its bottom to the bottom of the vessel at a point outside of the vertically downward projection of the roof and within the vertical downwardly projection of the sidewalls, and a foundation for the vessel having a portion beneath the point of the connection of the chord to the bottom, whereby stresses induced when said vessel is partially filled with the liquid are carried outwardly and downwardly by the chords to the foundation.

9. A vessel for storing liquids at substantially atmospheric pressure having a top, a bottom extending outwardly beyond the top, and sidewalls, the sidewalls being curved from the bottom to the top to equalize tension therein when the vessel is full of liquid and the angle at the juncture of the sidewall to the top being equal to the angle at the juncture of the sidewall to the bottom, there being truss members at intervals along the sidewalls connected to a substantially straight strut, said strut being connected at its top to the juncture of the sidewalls and the roof and at its bottom to the bottom of the vesse1 at a point outside of the vertically downward projection of the roof and within the vertical downwardly projection of the sidewalls, and a foundaftion for the Vessel having a portion beneath the point of the connection of the strut to the bottom, whereby stresses induced when said vessel is partially filled with the liquid are carried outwardly and downwardly by the struts to the foundation.

10. The vessel of claim 7 in which the top and bottom are substantially nat.

1l. The vessel of claim 7 in which the corners of the vessel are angular and are braced by a diaphragm welded thereto and to the bottom and roof of the vessel.

HARRY C. BOARDMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,622,787 Horton Mar. 29, 1927 1,809,013 Boardman' June 9, 1931 1,861,069 Smith May 31, 1932 2,273,601 Thomas Feb. 17, 1942 2,380,089 Ulm July 10, 1945 2,408,105 Starret Sept. 24, 1946 FOREIGN PATENTS Number Country Date 269,789 Germany Jan. 30, 1914 270,659 Germany Aug. 19, 1924 862,235 France Mar. 1, 1941 

